from turtle import setx,sety,xcor,ycor,pu,goto,pd,circle
def relative_move(x=None, y=None):
    if x is not None:
        setx(xcor() + x)
    if y is not None:
        sety(ycor() + y)

def absolute_move(x, y):
    pu()
    goto(x,y)
    pd()

def arc_line(arc,len,s):
    for i in range(s):
        circle(arc, len)  #上半弧度
        circle(-arc, len)  #下半弧度